For the purpose of enhancing evaporation efficiency, various methods have been used in a most of conventional evaporators. A multiple effective evaporator out of conventional evaporators is to improve the gradual degrading of a steam temperature every when the generated steam is one by one passed through the evaporators in the course of a reusing the generated steam. The improvement is to make an atmosphere pressure of a respective evaporating chamber low using a decompression pump. This requires paying a high expense and having many equipment sources. Further, in constituting a plural of evaporators a maximum number of evaporators are restricted by fourteen evaporators to carry out a multiple effective evaporation. A multiple injection evaporation method which is like as this method also has problems in that it is to have a reducing pressure which is the same problem as a multiple effective evaporation method and in a steam compression evaporation method it is uneconomic to compress a steam and to have a limit of a processing amount, as well as a big structure.